In addition to the classical filtration and softening, treatment with ozone or irradiation in the ultraviolet region plays an important part in water treatment. In connection with the manufacture of highly integrated cirucits in the electronics industry, the requirements imposed on rinsing water have been increased again. The permissible values for microbe counts and residual oxygen contents have been reduced further. The state of the art of high-purity water recirculation systems, including pretreatment of the water, has been described in numerous references (cf. R.A. Hango, "Deionized Water System", Solid State Technology, 1983, July, pages 107-111).
The ultraviolet radiators usually employed for sterilization are effective only in the path of the rays from the lamp and do not therefore represent an absolutely reliable protection. Although ozone treatment would eradicate this disadvantage, it introduces undesirable oxygen into the circulation system. The synergetic action of ozone and ultraviolet irradiation has been described (of., for example, R. Barker and F.M. Taylor "Oxydation of 2-propanol in Dilute Aqueous Solution by UV/Ozone", Poceedings of the Int. Conf., - The Role of Ozone and Waste-water Treatment, London, 13-14th November 1985).
It is known that oxygen is reduced by hydrogen at room temperature in the presence of catalysts (palladium), water being formed (cf. inter alia, F. Martinola, S. Oeckl and P. Thomas, "Catalytic Reduction of Oxygen in Water", Vom Wasser 65, 1985, pages 163-72, Translation).
Electrochemical cells containing a solid electrolyte in the form of a membrane composed of a plastic polymer (ion exchange) and suitable proceses for producing gaseous products have been described in numerous references. Such cells may advantageously be used to produce ozone (cf., for example, U.S. Pat. No. A 4,416,747; EP-B-0,068,522; H.P. Klein and S. Stucki, The Production of Ozone by Electrolysis and its Application in high purity Water Systems, Conference Proceedings, 7th Ozone World Congress, pages 110-115, 9th-12th September 1985, Tokyo).
The processes and equipment described above in general no longer meet the constantly increasing requirements for high-purity water circulation systems. There is therefore a need to refine the processes and develop them further.